I have noticed lately that while driving, especially around 40mph, when I let off of the accelerator the car jerks as if I were downshifting a manual transmission (mine is automatic BTW). My fear is that I'm losing my transmission but I want to hope for the best since about a year and a half ago I had to drop a new engine in, two weeks ago I had to replace a rear stuck caliper and just this past weekend, I replaced the intake manifold gasket. I'm hoping that it's just a choking problem since when I let off of the accelerator, the RPM's rapidly drop about 1500-2000. If the transmission goes on this car, it will be the last straw. This has by far been the most troublesome vehicle I have ever owned.

I don't know if its the same problem, but mine does that sometimes when I left of the gas pedal... and mine is a manual. It stays in gear, it just jerks when you let off (and when you reapply) the gas pedal if the clutch isn't in.

The engine mounts could be the issue since this is the second engine. However, today when I shifted into park after driving, the RPM's crept up to around 2500 and stayed. I popped the hood and pulled on the throttle cable a little bit and it went back down. When I got home I adjusted the throttle cable some with a few turns of the nuts and took care of the problem. Coincidentally, the chugging and jerking has been greatly reduced but it still does it right at about 40mph and has for quite some time.

i get the same thing dude. i have an automatic as well. it jerks and it feels like the car is slowing down a little. the gas pedal feels kinda "muddy". it happens around 40mph for me too but it doesnt do it all the time. after driving a while it either comes back or stops doing it. But i kinda realized it happens more when ive been accelerating harder than usual, ie: Merging or beating a yellow light

Yeah, I have noticed mine doing a little hesitation on accerleration. All of my motor mounts are pretty much blow (small cracks and completely dried out). I'll be headed to pull apart soon to see if I can find anything good. I am scared to see what the stealership has to offer. We looking $500 for all of them? More?

I understand what you are saying about the car jerking when letting off of the gas; you can add me to that list.

About the 40mph thing, is that in reference to the gas pedal thing, or are you referring to your engine running kind of sluggish. Mine runs real sluggish right at 40mph, as well as 2-3 mph up or down from 40. If I'm accelerating, it runs fine until about 38, than it kind of bogs down, and returns to running normal once I pass 42.

Is that what you are referring to? I would sure like to know what the hell that is.

From your symptom description, especially the throttle linkage adjustment, I'm thinking you may have a carboned-up throttle plate and it is "sticking" in the throttle bore and then quickly releasing when the return spring pressure exceeds the resistance.

With regards to the motor mounts, they're probably gone if it clunks or slams when it shifts up/down, if you hammer the gas, or if you're accelerating hard and it shifts during that. Personally, I never noticed any unusual slugglishness (my old car was slow as shit anyways).

On my last car (86 deville fwd) I was having similar problems, so I took it to a tranny shop. The mechanic took it around the block, and checked the engine under load (at a stop, hold the brake, and give it some gas, not enough to do a brake stand or anything bad). He said it was probably the mounts, so he took in the shop and put it on a lift, and showed me that the two front mounts were completely seperated. It ended up cost me close to 500$ to have them replaced, but that was due to the age of the car, the fact that it was a Cadillac (mounts were roughly 50-60 bucks each), and because they weren't sure which mounts they needed, so labour for trial and error. Should be cheaper on a newer and more common vehicle, like 80% of the cars made in the last decade.

One thing I did notice when I had the mount problem, and I've heard other people say as well, is that you can see the engine moving if the mount(s) are bust. Pop the hood, and get a buddy to watch the engine while you put it under load. You can kind of see the hood moving when your driving as well, but I'd advise watching the road ahead when you're rolling.

And I'd shop around before you take your car to a dealer (unless it's under warranty).

Okay so I pretty much agree with most of you guys here. I hardly post on this forum but this has been really bothering me as well. I only notice it the most on 40+mph or highway speeds. When I let off the acceleration it gives a little bump like i took cruise control off or something. When I reapply the acceleration, i get the same feeling again.

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